1. Field of the Invention
The present invention relates to a piping structure of a flexible tube. More particularly, the present invention relates to a structure for connecting a flexible tube to an attachment with a built-in motor rotatably coupled to the lower end of the main shaft ram for use in a machining center.
2. Description of the Related Art
Japan Published Examined Utility Model Application No. 4-45391 discloses a structure for wiring a signal line around a rotary table of a machining center. In this wiring structure, the machining center's rotary table and saddle are provided with internal and external sun gears, respectively. In addition, a plurality of bobbin-like planetary gears having a circular recess around their sides are engageably provided between the two sun gears. One end of the signal line is fastened to the rotary table with the other end fastened to the saddle. The signal line is doubled black around one of the planetary gears in such a manner that the signal line can be guided around the rotary table without slack as the planetary gears revolve due to the rotation of the table.
The above-described wiring structure, although effectively applicable to a flat cable and certain types of signal lines, has the disadvantage of requiring an extremely large planetary gear mechanism to guide a thick motor power line with a large minimum bending radius. Moreover, this wiring structure cannot be utilized with a power line inserted through a protective flexible tube laid around a rotor.